Heater



FIG. 1 is a front, right, perspective view of the heater;

FIG. 2 is a front view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is a left view thereof (the right side is a mirror image of the left); and,

FIG. 5 is a top view thereof.

The broken lines are for illustrative purposes only and form no part of the claimed design. 

We claim the ornamental design for a heater, as shown and described. 